The present invention relates generally to clutch mechanisms and more particularly to a clutch for engaging and disengaging a worm with and from a driven member such as a worm gear.
A worm drive has a number of advantages that can be of considerable utility in the functioning of an industrial robot. For example, a robot can be designed with a motor driven worm, with the driven member (such as a worm gear) being positively coupled to a tool for movement thereof. With the use of a control having a programmed sequence of commands, the motor can be driven in a sequence of desired directions and at desired speeds to cause the tool to be driven through a predetermined path of movement.
One advantage of a worm drive in such an application is that the positive, gear reduction character of the drive enables a relatively low torque and inexpensive motor to provide a considerable amount of force to the tool.
Another advantage of a worm drive is that the axes of the worm and worm gear are at right angles to each other so that the movement of the worm gear teeth is in a direction parallel to the axis of the worm. Thus, if any external force is exerted on the tool to move it from where it is, the force fed back to the worm gear will be applied to the thread of the worm in a direction parallel to the axis of the worm. Because of the relatively small pitch angle of the worm, very little radial force on the worm is required to hold the worm against the fed back axial force thereon.
At the same time, the ability of a worm drive to hold against external forces applied to the tool prevents the use of a worm drive in a manually teachable robot of the type wherein the tool is moved by hand through a desired path, with the sequential positions of the tool being used directly to make the program which will subsequently be used to move the tool through the desired path. In such an instance, the holding ability of a worm drive will prevent the tool from being moved by hand during the teach mode.
It is the primary object of the present invention to provide a clutch mechanism which can quickly and easily engage or disengage a worm and worm gear or other driven member. Such clutch mechanism, in a robot environment, will then enable the worm drive to be disengaged for manual movement of the tool in the teach mode and to be engaged for positive drive of the tool during the work mode.